All good things come to an end… Among the many, and varied, aspects discussed at ICCOSS over the past few days, I wanted to bring your attention to halogen–halogen bonding, which seems to be becoming quite popular. When a halogen atom engages in such a bond, its charge distribution changes a little, leading to a ‘polar flattening’ of the atom. The more electronegative side of one atom naturally engages in a halogen–halogen bond with what has become the more electropositive side of the other. Can these interactions be relied on to assemble building blocks? Can they be tuned in a controllable manner by judicious choice of the halogen?